Crank shaft grinding machine



Aug 27, 1935. c. H. AMlDON CRANK SHAFT GRINDING MACHINE Filed Sept. 19,1954 4 Sheets-Sheqt l Aug. 27, 1935. c. H. AMIDON CRANK SHAFT GRINDINGMACHINE Filed Sept. 19, 1934 4 Sheets-Sheet 21lllllllllllllllllllllll'lllh 3 ill 93 Aug. 27, 1935. c H A lb N2,012,263

CRANK SHAFT GRINDING MACHINE Filed Sept. 19, 1934 1 4 Shegts-Sheet 3Aug. 27, 1935. A D N 2,012,263

CRANK SHAFT GRINDING MACHINE '7 'Filed Se pL 19; 1934 4 Sheets-Sheet 4Patented Aug. 27, 1935 UNITED STATES 2,012,263 I CRANK SHAFT (mmnmcMACHINE Charles H. Amidon, Worcester, Mass, assignor.

to Norton Company, Worcester, Mass, a corporation of MassachusettsApplicatiomseptember 19, 1934, Serial No. 744,109

13 Claims.

The invention relatesto grinding machines,

. and with regard to its more specific features to a grindingmachine forgrinding crank shafts.

One object of the invention is to provide a grinding machine capable ofgrinding irregular bodies at a high rateof production. Another object ofthe invention is to provide a grinding machine capable of grinding allthrows of a crankshaft at a single operation. Another object of theinvention is to provide a grinding machine adapted to grinding cranksand similar articles to a high degree of precision. Another object ofthe invention is to provide a highly efiicient grinding machine. Anotherobject of the invention is to provide a grinding apparatus adapted toproduce precision results without the use of work-rests, thussimplifying the grinding operation. Other objects will be in partobvious,

or in part pointed out hereinafter.

The invention accordingly consists in the features of construction,combinations of elements, and arrangements of parts as will beexemplified in the structure to be hereinafter described and the scopeof the application of which will be indicated in the following claims.

In the accompanying drawings, illustrative of one of various possibleembodiments of the mechanical features of this invention,

Figure 1 is a front elevation;

Figure 2 is an end elevation, the machine being viewed as from theleft-hand side of Figure 1, certain machine parts being shown as Ibroken away to show other mechanism;

I Figure '3 is a viewon an enlarged scale of a device for holding theaxis of each grinding wheel at any one of a plurality of points in itsorbital path for use when it is desired to true one or more of thegrinding wheels; I f

Figure 4 isa'fragmentary view-showing the wheel truing or dressingdevice;

Figure 5 is a detailed view showing a pair of grinding wheels and theirmountings, one wheel and its support being illustrated in .section;

Figure 6 is a diagrammatic view illustrating the grinding of acrankshaft and the driving trains for wheel rotation, wheel orbitalmovement, and workpiece rotation; v

Figure 7 is an enlarged view, similar to Figure 5, showing a modifiedform of wheel mounting whereby the planes of rotation of the sev eralwheels may be adjusted relative to each other by a small amount;

Figure 8 is a sectional view taken on the line 8--8 of Figure '7.

As conducive to a clearer understanding of the present invention, I notethat the regular practicein grinding crankshafts has involved thegrinding of the several pins or throws successively. Machines which haveheretofore been provided for grinding crankshafts according to suchmethod have included mechanisms for successively positioning the samewheel against different throws and for supporting the work-piece. Withthe very best arranged and organized of such machines the setting up forgrinding of successive' crank-throws has nevertheless involved asubstantial amount of time. The present invention succeeds in performingat a single operation successfully that which, according to the usualprior practice required a plurality of operations.

Referring now to Figures 1 and 2, I provide a machine base I l uponwhich'is mounted a table or carriage l2 by means of suitable ways on theunder side of the table, not shown, and cooperating ways l3, l4 formedin the machine base II. The table or carriage l2 may be movedlongitudinally of the machine base .I l by means of a hand wheel l5which is connected, through suitable gearing not shown, to a drivinggear l6 that meshes with a rack I'I fastened to the under side of thetable or carriage l2, Although, so far as certain fea- .which is hereshown as an automobile crankshaft,

is carried by centers 2| and 22, the latter being mounted in the usualadjustable tail-stock 23 having a hand towards and away fromthe-work-piece, together with locking device 25 to lock the center 22 inadjusted position. This tail-stock 23 is in turn adjustably mounted formovement parallel to the axis of rotation of the work-piece on thetablel 2, and may be secured in adjusted position by means of clamping bolts26 In order that this machine may be to a large extent universal and tofacilitate removal of the machine parts from the base when desired, andfor simplicity in setting up the machine, I prefer to mount the headcenter 2| in a head-stock 30 which is independent of the table l2 butwhich wheel 241:0 move the center 22 table I2 rests upon and whichhead-stock has cooperating ways formed therein and designated by thenumerals 3| and 32 on Figure 2. By reason of this construction variousdriving mechanisms hereinafter referred to may be lined up to performtheir functionwithout undue friction, andonce the desired position ofthe head-stock 30 is. achieved it may be bolted in place by means ofholding bolts 33.

Still referring to Figure l, the center 2| is, as in lathe practice,removably positioned in a workspindle 34, to the outer end of which issecured a driving plate 35. [The spindle 34 is suitably J'ournaled forrotation in the head-stock 30 and is rotated as will hereinafter bedescribed.

' The majority of modern automobile crankshafts have integrally forged'therewith at one end a driving plate 36, to be secured ultimately to theautomobile flywheel, and this driving plate 36 has one or more holestherein and usually one hole at least is located to precision limits afixed radial distance from the crankshaft center, and I find suchcrankshafts may readily be driven by locating a driving pin 31 removabsecured to the driving plate 35 in such hole in the driving plate 36,but for other types of crankshafts, or for this type if desired, theusual lathe dog may be employed. a Assuming now that the spindle 34 isrotated, the table I2 and the head-stock 30 having been fixed inposition and the centers 2| and 22 engaging the crankshaft 20, and thedriving pin 31 fixed in position as described, with the locking device25 in locking position, the crankshaft 20 will be rotated, andsuccessive crank-throws 4|, 42, 43 and 44 will partake of circularorbital movements, with diurnal motion equal in angular velocity to theangular velocity of their orbital motion respectively. I haveillustrated herein a crankshaft with successive throws angularly dis- Iplaced 90 deg. from the preceding throw in the orbital path, but themuch used four-throwcrankshaft with all throws in a plane, may be groundon the present machine, and so also may any type of sixortwelve-cylinder crankshaft, such as the familiar type of crankshaftemploying the one hundred and twenty degree angle of displacement.

For the grinding of the crankshaft 20 or any other work-piece accordingto the present invention, I provide a plurality of grinding wheels 5|,52, 53 and 54 (see now Figure 6) which I cause to rotate diumally andalso to move orbitally in a circular motion complementary to that of theseveral throws 4|, 42, 43 and 44, that is with the orbital movement ofeach grinding wheel always in phase with the orbital movement of thethrow it is grinding, and having the same radius and angular velocity. Ifurther provide means colleca tively to displace all the orbits of thegrinding wheels towards the orbits of the crank-throws to produce acutting in-feed.

Still referring to Figure 6, I provide an electric motor 60 to which iscoupled ashaft 6| by means of a coupling 62, the shaft 6| being mountedin suitable bearings 63 and-64, and the shaft 6I having affixed to itfour pulleys I I, 12, I3 and I4 which are connected by belts I5, 16, TIand "to pulleys 8|, 82, 83 and 84 attached to the several grindingwheels 5|, 52, 53 and 54. Likewise mounted on the shaft 6|, but notfastened thereto. are arms 85, 86, 81 and 88 which mount idler pulleysSI, 92, 83 and 84 that serve to tension the Figure .8)

. 2,012,263 'rests upon the same ways I3 and I4 that the belts 15, I6,I1 and I8, springs 95, 86, 91 and 98 providing the required tefision.

Referring now to Figure 5, I provide for the machine a number ofcrankshafts I 00, each one of which is the counterpart of a crankshaftto be ground, so far as angular position of crank throws or pins andradius of throw thereof and longitudinal spacing of throws arevconcerned. Each crankshaft I00 is-preferably an' integral forging, andhas pins IOI, I02, I03 and I04 upon which are mounted the pulleys 8|,82, 83 and 84 respectively, these pulleys being each split pulleys, thatis formed of a pair of similar halves for assembly purposes (this typeof construction being illustrated with respect to themodification, inPulleys 8|, 82, 83 and 84 fit nicely between shoulders II 0 and III onthe respective .throws IOI --I04, and these pulleys constitute mountingsfor the respective grinding wheels 5I54, which are thereby freelyrotatable on the several pins IOI| 04. The mounting for each wheelincludes likewise an additional removable split clamping plate II2, eachone secured to its corresponding combined pulley and mounting 8I84 bymeans of bolts I|3,'and when it is desired to replace a worn grindingwheel with a new one, the two halves of the plate II2 are first removed,whereupon the grinding wheel may be moved sideways off the shoulder onitspulley mounting, which frees the latter, the grinding wheels havingholes therein sufficiently large to pass over the throws of thecrankshaft I00.

' Referring now to Figure 2, I provide a crossslide or table I20 such ashas been heretofore provided in grinding machines, and mounted on ways,not shown, provided therein; and on the base I I for movementperpendicular to the movement of the carriage I2 on ways I3 and I4. Itis by movement of the cross-slide. I20 that the cutting action issecured, and the cutting feed which may be, continuous, if desired, isachieved in any usual or desired manner, such as by means of across-feed screw I2| mounted, integrally formed on, or securedto a shaftI22, which is mounted in suitable journals or bearings notshown,provided in the machine base II, and which is actuated by means ofa hand wheel I23 (see also Figure 1) and associated mech- 'anismincluding interposed gearing and shields,

stop devices I24 and the like, all ofwhich may be of any usual ordesired form, for example such as shownin U. S. Letters Patent No.762,838'granted to Charles H. Norton. By such a mechanism a graduatedand controlled,

' and if desired a continuous cross-feed of the cross-slide I20 may besecured, and such move- 'ment is a precision one, and relativelyspeaking a slow one or'one composed of ,minute successive increments. Asshown in Figure 2, the motor 60is 'mounted'oncross-slide I20; likewisemounted thereon are the bearings 63 and 64 of the shaft 6|. Each crank I00 provided for the machine, in addition to the two, four, six or anyother number of crank-throws orpins provided, has a. pair of endtrunnions I25 and I26.v

Referring to Figure 2, to the trunnion I25 is attached a worm wheel I28.The trunnion I25 is removably mounted in a journal I30 which is atwo-part journal for removal of the crankshaft |00; the other trunnion26 is removably mounted in a two-part journal I3I. The bottom half ofeach of the.journals I30 and I3I is fastened'to the cross-slide I20, 8.fixed distance from the axis of the shaft 6|, although, adjustably .onthe axis of the crankshaft I00.

Thus all of the grinding wheels and the dIiVr' ing mechanism thereforare carried on the crossslide I20 so that they may be caused to approachand recede from the work-piece collectively at will.

Referring now to Figures 2 and 6, I provide mechanism for rotating thework-piece crankshaft 20 and the grinding 'wheel supporting crankshaft Isynchronously, that is at the same angular velocity, and I furtherprovide means for synchronizing their phases. The work-spindle 34 hasrigidly secured to it a worm wheel I35, and with this worm wheel meshesa worm I36 which is afiixed to a shaft I31 that is journaled in abearing, not shown, in the work-head 30. The shaft I31 extends through apair of bearings I38 carried by a standard -I39 projecting upwardly fromthe cross-slide I20, and the shaft I31 likewise passes through a coupleof bearings I40 carried by a casing I4I also secured tothe cross-slideI20, which casing I4I likewise supports a bearing I42 for a shaft I43that is in line with and adapted to be coupled to the shaft 6|, by meansof a clutch to be described. Meshing with the worm wheel I28 is a wormI44 which is held in a fixed position so far as translation is concernedwith respect to the cross-slide I20 by the bearings I36.

The worm I44 is splined and a long key I45 on the shaft I31, or anysimilar device to transmit angular motion without transmittingrectilinear motion, causes the shaft I31 to drive the worm I44 andtherefore the worm wheel I28.

The casing I4I contains a large worm wheel (not shown) which isrestrained from movement relative to the casing by the bearings I40,I40, the shaft I31 having a'long key I46 cooperating with a spline insaid worm wheel, the purpose of this construction for transmitting powerbeing the same as with respect to the worm I44. Fastened to the shaftI43 is a worm, not shown, which meshes with the aforesaid worm wheel todrive ,7

the same. The shaft I43 is normally connected by a positive dog clutch I41 to the shaft 6I, but may be disconnected therefrom by means of alever I48 having a pin I49 fitting in a groove I50 formed in movablepart II of the clutch I41.

The movable part I5'I is splined to the shaft 6| while the abutting partI52 of the clutch I41 is fixed to its shaft I43.

When the clutch I41 is engaged and the motor 60 is running, power istransmitted along" the shaft 6 I through the clutch I41, and to theshaft I31,'thus to drive both cranks 20 and I00, and as the worms I36and --I44 are of the same size and pitch, and likewise the worm wheelsI35 and I28 are of the same size and pitch, the crankshafts are rotatedat the same angular velocity, and since the worm wheels are so locatedon their respective shafts as to maintain corresponding crank-throws inthe same phase relationship, and the two cranks are similar asheretofore pointed out, and their throws have the same radius, itfollows that the orbital movement of each grinding wheel traces a circlesimilar to the orbital movement of each throw of the crank 20 and in thesame phase relationship. By reason of the gear ratio which will besufiiciently apparent from the accompanying drawings, the diurnal motionof each grinding wheel is very much greater than its orbital velocity,and further by reason of the large diameter of the grinding wheels ascompared with diameter of crank-throws to be ground, a high peripheralgrinding speed is achieved. Assuming a constant diurnal velocity of thegrinding wheels and aconstant angular to .the work surface. By reason ofthe orbital motion, however, there is a tendency to change the velocityof each grinding wheel as the grinding wheel pulleys 0|, 82, 83 and 84approach and recede from the driving pulleys 1|, 12, 13 and 14.

By using a non-positive drive for the wheels-5|,

52, 53 and 54 I find that their inertia of rotation checks thistendency, at least sufiiciently so that no harmful effects result.

A crank I00 having been chosen which has throws the same as those ofacrankshaft to be ground, as stated, and grinding wheels having beenmounted on such crank I00 as shown and described, the work-piece crank20 is mounted in place between the centers 2|, 22 and the driving pin 31is inserted in the hole in the plate 36. As-' suming that the center 2Iis of a length to dispose several throws"4 I 42, 43 and 44 opposite thegrinding wheels, the work-piece crank 20 may then be ground to finishedsize by starting the motor. 60 and then advancing the cross-slide I20 byturning the hand wheel I23. On account of the fact that the orbitalmovement of the grinding wheels is the same as that of the crank-throwsto be ground, the planes of tangency between the sev-' ccsfively by allportions of the respective throws on account of their diurnal motion.Thus by advancing the grinding wheels to contact with the severalthrows, all of them may be ground by an equal amount and to' a givendiameter. If desired, a continuous in-feed of the grinding wheels may beemployed, in connection with a dwell at the end of such feed to continuethe grindinguntil the effect of pressure in the several machine parts isremoved. This is called grinding out the spar ployed, if desired. Inorder to avoid, as much as possible, grinding lines in the work-piece,the grinding wheels should be of-an even texture and have a relativelyhard surface.

After the machine is once set up, similar cranks An intermittent feedmay also be em- 1 may be introduced into the machine merely by limits,they should be trued. I provide truing mechanism to true the wheels 5I54 without removing them from themachine.

Referring now to Figures 1 and 4, a truing hold er I60 has therein a rodI6I having screw threads, not shown, cooperating with internal threadsin the holder I60. The rod I6I has'a diamond I62 in one end thereof, andon the other end a knob I63 by the angular adjustment of which theposition of the diamond I62may be adjusted to within precision limits.The holder I60 has ways I64 fitting ways I65 providedonthe table I2.' Anintegralbracket I66 carries a pinion gear I61 cooperating with a rackI68 afiixed to the table I2 as shown in Figures 1 and 4 which serves asan adjusting means for, positioning the holder relative to the table I2.Referring to Figure 1, the holder I60 is held in adjusted position onthe table 82 by means of a binder bolt I10, andby tightening this boltthe holder I 69 may be rigidly secured to the table I2. Prior to suchrigid clamping of the parts together, however, the diamond I62 may beadjusted to exactly the desiredposition relative to the table I2 in alongitudinal direction by turning the bolt-headed stud I'll upon whichthe pinion I61 is mounted.

. In connection with the truing of the wheels, I provide means torestrain the orbital movement thereof while permitting their diurnalmotion. Referring to Figure 1, an index plate I15 is secured to the endof crankshaft I00, this index plate H15 having a number of indexnotchesI16 equal to the number of throws of the crank to be ground andpositioned angularly on said index plate by angles corresponding to thedisplacement of the several throws. When it is desired to true thegrinding wheels and to insure the grinding of.each throw 4 I, 42, 43 and44 to the same diameter, clutch I 41 is first released, and then theshaft 19 is turned (by manually turning the shaft I43, for example)until one of the notches is engaged by a detent I11 mounted, as shown inFigures 2 and 3, in a portion of the bracket I39. This restrains orbitalmovement of the grinding wheels, and one or more of them are in aforward position. The dressing holder I 60 having been secured inposition as described, the motor 69 may be started, and then by turningthe hand wheel 55, the diamond I62 may be traversed with whatever wheelis at that time farthest forward. It is noted that the crank -20 willpreferably not be located in the machine at this time, and it is furtherobserved 'that coarse longitudinal adjustments of. the diamond holdermaybe made by positioning it in the desired place on the table I2, whilethe traversing action of the diamond is better achieved by moving thetable afterthe dressing device is locked in position. To insure contactbetween wheel and-diamond, screw I63 may be turned.

Having trued one -of the four (more or less) wheels, the detent I11 iswithdrawn as by, pulling the action of a spring I80, and the shaft Irotated until the next notch I16 comes under the e e the notch and it isnoted that the detent is preferablyof wedgeshape, as shown, to cooperegate with the wedge-shaped notch to determine accurately the position ofthe several grinding wheels in their orbits.

A second wheel having been positioned forward, it is now trued-bytraversing the table I2 through the medium of the hand wheel I 5. Insome cases this may be done without readjusting the bracket I60 on thetable I2, and in other cases such' readjustment will be effected, butthe position of the diamond I 62 with respect to the cylinder containingall of the orbits should remain the same, which will be the case if theadjustment of the knob IE3 is undisturbed.

If the several wheels are successively trued as indicated, both byreason of the fact that their orbits all lie in the same cylinder, andby reason further of the fact that the table I2 moves in a line paralleltothe axis of thatrcylinder, and wherefore parallel to all of theelements thereof, the several grinding wheels will be dressed and truedto the same diameter which, under the conditions and with the machine asdescribed; will insure, in succeeding grinding actions, the productionof ground crank-throws all of the same diameter.

Subsequent to the truing operationsthe detent I11 should be withdrawn bypulling out the knob I19, and the detent may be held in withdrawnposition by giving the knob I19 a partial turn. The knob I19 and thedetent I 11 are connected by a shaft I8I projecting laterally from whichis a pin I82 slidably in'a slot I83. Pin I82 and slot 483 serve to alignthe detent I11 in its operative position, and upon withdrawal of thedetent the pin I 82 moves out of the slot I83 and after the parts aregiven a partial turn the pin I82 engages the front face of a bearingportion I84 thus to Hold the detent withdrawn. The machine is then readyfor the introduction of a crankshaft 20 to be ground, and orbitalmovement of the crankshafts 20 and I00 is resumed upon engagement of theclutch I41.

Figures 7 and 8 illustrate a modification in the wheel mountingmechanism. A wheel mounting crankshaft IIlIla. is provided whose throwsor pins represented by pins Ill2a, I031: and Ma have threaded portions I02b, I03!) and Nb upon which are mounted spanner nuts I99 engagingwashers l9I which engage the pulley mountings 8 I, 82, 83 I and 84respectively, the other side of said pulley wheel mountings beingengaged by washers I92 that are backed up by springs I93 located in thecrank-arms as shown in Figures 7 and 8. By turning the spanner nuts I90one way or the other the longitudinal position of each wheel maybeadjusted sufliciently to cause each wheel to be cated accurately withrespect to the fillets on the crank-throws 4|, 42, 43 and 44 which wereproduced in the previous operation, either a lathe operation or aforging operation or otherwise.

One adjustment laterally of all the grinding wheels 5|, 52, 53 and 54will probably suflice for the grinding of any given lot of crankshaftsin actual production practice. It should be noted that-this means ofadjusting the position of the several grinding wheels permits the wheelsto split the spar on all throws thus achieving economy so far as wear ofthe grinding wheels is concerned. a knob I19 thus withdrawing saiddetent against It will thus be seen that there has been provided by thisinvention with many thoroughly practical advantages, are successfullyachieved.

As various possible embodiments may be made of the above invention andas many changes might be made in the embodiment above set forth, it isto be understood that all matter hereinbefore set forth, or shown in theaccompanying drawings, is to be interpreted as illustrative and not in alimiting sense.

1. A grinding machine comprising, in combination, a crankshaft with aplurality of throws, a plurality of grinding wheels one on each ofseveral of said throws, a rotatable mounting for a work-piece, means torotate the said mounting, means synchronized with said last-named meansto rotate said crankshaft, and flexible means to rotate each of saidgrinding wheels.

2. A grinding machine comprising, in combination, a plurality ofgrinding wheels, individual mounting means for each of said grindingwheels movable through predetermined paths, a rotatable mounting for awork-piece, means to rotate said last-named mounting, means to rotateeach of said individual mountings for said wheels through theirpredetermined paths and synchronously with said mounting for saidwork-piece. and

an apparatus in which the various objects hereinabove set f rth, to thdetent I11. The spring I89 causes the detent to o ge er ing wheel,

means to rotate each of said wheels on its mount- 3. A grinding machinecomprising, in combination, agrinding wheel, means to rotate orbitallysaid grinding wheel, means to rotate diurnally said grinding wheel,means to rotate a work-piece on an axis entirely outside the orbit ofsaid grindand means to cause said work-piece to approach said orbit bygrinding increments.

4. A grinding machine comprising, in tion, a plurality of grindingwheels, a, mounting for each grinding wheel, means to move the axis ofeach grinding wheel through predetermined courses at equal angularvelocities, means to rotate each grinding wheel on its axis, means toarrest any grinding wheel at a. predetermined angular position in itscourse which is the same for all said wheels, means to locate a dressingdevice at such position, and means to traverse said wheel with'saiddressing device.

5. A grinding machine comprising, in combination, a grinding wheel,means to rotate said grinding wheel orbitally, means to rotate saidgrinding wheel diurnally at a velocity greatly-in excess of the velocityof its orbital motion, means to rotate a work-piece orbitally, and meansto rotate said work-piece diurnally at the same angular velocity as theorbital motion.

6. A grinding machine comprising, in combina-.

tion, a plurality of grinding wheels means to rotate all of saidgrinding-wheels in the same orbital path maintaining their ascensionsdifferent and their relative hour angles the same, and

means to rotate each wheel diurnallyat substantially a constant angularvelocity.

'7. In a grinding machine as claimed in claim 6, the combination withthe parts thereinspecified, of precision means to true each wheel to thesame diameter.

8. In' a grinding machine as claimed in claim 6, the combination withthe parts therein specified, of means for arresting any of the saidgrinding wheels at a given and at the same hour angle combinawhilemaintaining its diurnal motion, a dressing device, means to traversesaid dressing device relative to the grinding wheel and in a lineperpendicular to the plane of any orbit, and means to adjust theposition of said dressing device.

9. In a grinding machine, a drive shaft, a plurality of pulleys on saiddrive shaft, a pair of separated journals in a line parallel to saidshaft, a member having a plurality of in said 'ournals for rotation, agrinding wheel mounted ior rotation on each pin, a pulley aflixed toeach grinding wheel, each of said first-named pulleys being in line witha. pulley for a grinding wheel, flexible driving means connecting theseveral sets of pulleys, and means driven from said shaft for rotatingsaid member.

10. In a grinding machine as claimed in claim 9, the combination withthe parts therein specifled, of a work-piece spindle parallel to saidjournals, and means to drive said spindle at the same angular velocityas and in the same phase relation as said member.

11. In a, grinding machine 9, the combination with the partsthereinspecified, of a work-piece spindle parallel to said journals,means to drive said spindle at the same angular velocity and in the samephase relation as said member, a dressing device, a mounting for saiddressing device to move it parallel to the axis of said journals, andmeans to arrest said shaft at any one of a plurality of positions.

12. A mounting for a plurality of grinding wheels comprising a, pair oftrunnions mounted in line, a plurality of pairs of crank-arms, aplurality of pins each pin detachably mounted between a pair ofcrank-arms, and a plurality of wheel mounting members each journaled ona pin. F

13. In a mounting as claimed in claim 12, the combination with the partstherein specified, of means for adjusting axially on its pin -one ormore .wheel mounting members.

CHARLES H. AMIDON.

axis pins mounted as claimed in claim

